Hyperion Mobility Testing

1
Hyperion Mobility Testing

• Dimi Apostolopoulos
• Michael Wagner
• Kevin Peterson
• July 28, 2003

2
Lab and Field Differences

• Current limits increased to 5 A continuous
• Rover mass 140 kg in the lab, 180 kg in field

3
Drawbar Pull Tests

• Drawbar pull is the force a vehicle can pull on a
  given soil
• The drawbar pull is measured by attaching the
  robot to a load cell and steel cable
• The robot is driven until the cable is tensioned
  and its wheels begin to slip
• The drawbar pull is the maximum force sensed by
  the load cell

4
Drawbar Pull Tests

• Drawbar pull is a useful metric because it can be
  used to find the maximum climbable slope for a
  given soil type
• Max slope atan(DP / weight)

Performed tests in cohesionless sand This soil
provides very little traction, similar to regions
of loose sand seen in the Atacama
5
Drawbar Pull Tests Results

1. Robot driving normally
2. Cable tension rapidly increases
3. Wheels slipping
4. Motion controller fault, at least one wheel stops
   servoing
5. Robot reverses, cable goes slack

c
Max DP 550 N Max slope 22 deg
d
b
e
a
6
Flat Floor and Climbing Tests

• Torque is calculated through the following
  equation
• T
• These torque measurements are most accurate when
  robot driving straight and at higher velocities

h I V
h 0.35
v / r
7
Flat Concrete Floor Power
8
Flat Concrete Floor Torque
9
20-cm Obstacle on Concrete Floor
10
Sandbox Power
11
Sandbox Torque
12
20-cm Obstacle in Sandbox
13
Flat Desert Terrain - Power
14
Flat Desert Terrain - Torque
15
10 cm Obstacle in Desert
16
Slope Climbing Tests
17
Slope Climbing 10 deg
Wheels climbing onto ramp
Entire robot climbing ramp
35 Nm
Wheels climbing onto ramp
Entire robot climbing ramp
20 Nm
18
Slope Climbing 30 deg
Entire robot climbing ramp
50 Nm
Entire robot climbing ramp
65 Nm
19
Slope Climbing in the Desert 10 deg
20
Slope Climbing in the Desert 14 deg
21
Maximum Obstacle Climb in the Desert

1. Robot is stopped
2. Left front wheel starts to climb
3. Left front wheel peaksthe obstacle at a height
   of 0.239 meters
4. All four wheels are on flat ground, left rear
   wheel starts to climb
5. Left rear wheel peaks the obstacle
6. Left rear wheel hits the ground and bounces

b
e
a
c
f
d
22
Rolling Resistance Comparisons

• Rolling resistance is the ratio of tractive force
  to vehicle weight
• Tractive force is dependent on soil properties
• Rolling resistance in sandbox 0.03
• Rolling resistance on concrete floor 0.02
• Rolling resistance on ramp 0.26
• Rolling resistance in the desert 0.08